Memory arrays having substantially vertical, adjacent semiconductor structures and the formation thereof

ABSTRACT

Memory arrays and methods of their formation are disclosed. One such memory array has memory-cell strings are formed adjacent to separated substantially vertical, adjacent semiconductor structures, where the separated semiconductor structures couple the memory cells of the respective strings in series. For some embodiments, two dielectric pillars may be formed from a dielectric formed in a single opening, where each of the dielectric pillars has a pair of memory-cell strings adjacent thereto and where at least one memory cell of one of the strings on one of the pillars and at least one memory cell of one of the strings on the other pillar are commonly coupled to an access line.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/836,853, titled “MEMORY ARRAYS HAVING SUBSTANTIALLY VERTICAL,ADJACENT SEMICONDUCTOR STRUCTURES AND THE FORMATION THEREOF,” filed Jul.15, 2010 (allowed), which is commonly assigned and incorporated in itsentirety herein by reference.

FIELD

The present disclosure relates generally to memories, and, inparticular, in some embodiments, the present disclosure relates tomemory arrays having substantially vertical, adjacent semiconductorstructures and the formation thereof.

BACKGROUND

Memory devices are typically provided as internal, semiconductor,integrated circuits in computers or other electronic devices. There aremany different types of memory including random-access memory (RAM),read only memory (ROM), dynamic random access memory (DRAM), synchronousdynamic random access memory (SDRAM), and flash memory.

Flash memory devices have developed into a popular source ofnon-volatile memory for a wide range of electronic applications.Non-volatile memory is memory that can retain its data values for someextended period without the application of power. Flash memory devicestypically use a one-transistor memory cell that allows for high memorydensities, high reliability, and low power consumption. Changes inthreshold voltage of the cells, through programming (which is sometimesreferred to as writing) of charge storage structures (e.g., floatinggates or charge traps) or other physical phenomena (e.g., phase changeor polarization), determine the data value of each cell. Common uses forflash memory and other non-volatile memory include personal computers,personal digital assistants (PDAs), digital cameras, digital mediaplayers, digital recorders, games, appliances, vehicles, wirelessdevices, mobile telephones and removable memory modules, and the usesfor non-volatile memory continue to expand.

A NAND flash memory device is a common type of flash memory device, socalled for the logical form in which the basic memory cell configurationis arranged. Typically, the array of memory cells for NAND flash memorydevices is arranged such that the control gate of each memory cell of arow of the array is connected together to form an access line, such as aword line. Columns of the array include strings (often termed NANDstrings) of memory cells connected together in series, source to drain,between a pair of select lines, a source select line and a drain selectline.

A “column” refers to a group of memory cells that are commonly coupledto a local data line, such as a local bit line. It does not require anyparticular orientation or linear relationship, but instead refers to thelogical relationship between memory cell and data line. The sourceselect line includes a source select gate at each intersection between aNAND string and the source select line, and the drain select lineincludes a drain select gate at each intersection between a NAND stringand the drain select line. Each source select gate is connected to asource line, while each drain select gate is connected to a data line,such as column bit line.

In order for memory manufacturers to remain competitive, memorydesigners are constantly trying to increase the density of memorydevices. Increasing the density of a flash memory device generallyrequires reducing spacing between memory cells and/or making memorycells smaller. Smaller dimensions of some device elements may causeoperational problems with the cell. For example, the channel between thesource/drain regions becomes shorter, possibly causing severe shortchannel effects.

One way of increasing the density of memory devices is to form stackedmemory arrays, e.g., often referred to as three-dimensional memoryarrays. For example, one type of three-dimensional memory array includesa plurality of traditional “two-dimensional” arrays, such as NAND memoryarrays, stacked vertically one atop the other, with the memory cells ofeach memory array being silicon-on-sapphire transistors,silicon-on-insulator transistors, thin film transistors, thermoelectricpolymer transistors, semiconductor-oxide-nitride-oxide-semiconductortransistors, etc. Another type of three-dimensional memory arrayincludes pillars of stacked memory cells, e.g., forming vertical NANDstrings.

For the reasons stated above, and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art foralternative stacked (e.g., three-dimensional) memory arrays.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a memory system, according to anembodiment.

FIGS. 2A-2D are cross-sectional views of a memory array during variousstages of fabrication, according to another embodiment.

FIGS. 3A-3D are cross-sectional views respectively corresponding toFIGS. 2A-2D.

FIGS. 4A-4E are cross-sectional views of a memory array during variousstages of fabrication, according to another embodiment.

FIGS. 5A-5E are cross-sectional views respectively corresponding toFIGS. 4A-4E.

FIG. 6 is a cross-sectional view of a memory array, as viewed from thetop, according to the prior art.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown, byway of illustration, specific embodiments. In the drawings, likenumerals describe substantially similar components throughout theseveral views. Other embodiments may be utilized and structural,logical, and electrical changes may be made without departing from thescope of the present disclosure. The following detailed description is,therefore, not to be taken in a limiting sense, and the scope of thepresent disclosure is defined only by the appended claims andequivalents thereof. The term semiconductor can refer to, for example, alayer of material, a wafer, or a substrate, and includes any basesemiconductor structure. “Semiconductor” is to be understood asincluding silicon-on-sapphire (SOS) technology, silicon-on-insulator(SOI) technology, thin film transistor (TFT) technology, doped andundoped semiconductors, epitaxial layers of a silicon supported by abase semiconductor structure, as well as other semiconductor structureswell known to one skilled in the art. Furthermore, when reference ismade to a semiconductor in the following description, previous processsteps may have been utilized to form regions/junctions in the basesemiconductor structure, and the term semiconductor can include theunderlying layers containing such regions/junctions. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present disclosure is defined only by the appendedclaims and equivalents thereof. The following detailed description is,therefore, not to be taken in a limiting sense.

FIG. 1 is a simplified block diagram of a NAND flash memory device 100in communication with a processor 130 as part of an electronic system,according to an embodiment. The processor 130 may be a memory controlleror other external host device.

Memory device 100 includes an array of memory cells 104, according toembodiments of the disclosure. For example, memory array 104 may includepillars, with each pillar having a pair of strings (e.g. NAND strings)of serially coupled memory cells thereon.

A row decoder 108 and a column decoder 110 are provided to decodeaddress signals. Address signals are received and decoded to accessmemory array 104.

Memory device 100 also includes input/output (I/O) control circuitry 112to manage input of commands, addresses, and data to the memory device100 as well as output of data and status information from the memorydevice 100. An address register 114 is in communication with I/O controlcircuitry 112, and row decoder 108 and column decoder 110, to latch theaddress signals prior to decoding. A command register 124 is incommunication with I/O control circuitry 112 and control logic 116 tolatch incoming commands. Control logic 116 controls access to the memoryarray 104 in response to the commands and generates status informationfor the external processor 130. The control logic 116 is incommunication with row decoder 108 and column decoder 110 to control therow decoder 108 and column decoder 110 in response to the addresses.

Control logic 116 is also in communication with a cache register 118.Cache register 118 latches data, either incoming or outgoing, asdirected by control logic 116 to temporarily store data while the memoryarray 104 is busy writing or reading, respectively, other data. During awrite operation, data is passed from the cache register 118 to dataregister 120 for transfer to the memory array 104; then new data islatched in the cache register 118 from the I/O control circuitry 112.During a read operation, data is passed from the cache register 118 tothe I/O control circuitry 112 for output to the external processor 130;then new data is passed from the data register 120 to the cache register118. A status register 122 is in communication with I/O controlcircuitry 112 and control logic 116 to latch the status information foroutput to the processor 130.

Memory device 100 receives control signals at control logic 116 fromprocessor 130 over a control link 132. The control signals may includeat least a chip enable CE#, a command latch enable CLE, an address latchenable ALE, and a write enable WE#. Memory device 100 receives commandsignals (which represent commands), address signals (which representaddresses), and data signals (which represent data) from processor 130over a multiplexed input/output (I/O) bus 134 and outputs data toprocessor 130 over I/O bus 134.

For example, the commands are received over input/output (I/O) pins[7:0] of I/O bus 134 at I/O control circuitry 112 and are written intocommand register 124. The addresses are received over input/output (I/O)pins [7:0] of bus 134 at I/O control circuitry 112 and are written intoaddress register 114. The data are received over input/output (I/O) pins[7:0] for an 8-bit device or input/output (I/O) pins [15:0] for a 16-bitdevice at I/O control circuitry 112 and are written into cache register118. The data are subsequently written into data register 120 forprogramming memory array 104. For another embodiment, cache register 118may be omitted, and the data are written directly into data register120. Data are also output over input/output (I/O) pins [7:0] for an8-bit device or input/output (I/O) pins [15:0] for a 16-bit device.

It will be appreciated by those skilled in the art that additionalcircuitry and signals can be provided, and that the memory device ofFIG. 1 has been simplified. It should be recognized that thefunctionality of the various block components described with referenceto FIG. 1 may not necessarily be segregated to distinct components orcomponent portions of an integrated circuit device. For example, asingle component or component portion of an integrated circuit devicecould be adapted to perform the functionality of more than one blockcomponent of FIG. 1. Alternatively, one or more components or componentportions of an integrated circuit device could be combined to performthe functionality of a single block component of FIG. 1.

Additionally, while specific I/O pins are described in accordance withpopular conventions for receipt and output of the various signals, it isnoted that other combinations or numbers of I/O pins may be used in thevarious embodiments.

FIGS. 2A-2D are cross-sectional views of a portion of a memory array200, during various stages of fabrication. FIGS. 3A-3D arecross-sectional views respectively corresponding to FIGS. 2A-2D. Memoryarray 200 may form a portion of memory array 104 of FIG. 1.

FIG. 2A is a cross-section (cross-hatching omitted) of memory array 200taken along line 2A-2A of FIG. 3A that is a cross-section(cross-hatching omitted) taken along line 3A-3A of FIG. 2A. In general,the formation of the structure of FIG. 2A may include forming adielectric 204 over a semiconductor 202 that, in some embodiments, maybe comprised of silicon that may be conductively doped to have a p-typeor n-type conductivity. Dielectric 204 may be, for example, formed froman oxide, e.g., silicon oxide, an oxynitride, e.g., silicon oxynitride,etc.

A sacrificial material, e.g., dielectric 206 ₁, is then formed overdielectric 204; a dielectric 208 is formed over dielectric 206 ₁; and asacrificial material, e.g., dielectric 206 ₂, is formed over dielectric208. Dielectrics 208 and 206 ₂ are then alternately formed until asacrificial material, e.g., dielectric 206 ₃, is formed over adielectric 208, as shown in FIG. 2A. A hard mask (e.g., a dielectriccap) 210 is then formed over dielectric 206 ₃. For some embodiments,dielectrics 208 may be same material as the material of dielectric 204,e.g., dielectrics 208 may be formed from an oxide, e.g., silicon oxide,an oxynitride, e.g., silicon oxynitride, etc. As one example, wheredielectrics 204 and 208 are an oxide or oxynitride, the dielectrics 206and hard mask 210 may be nitride to facilitate selective removal insubsequent processing. Because of the sacrificial nature of dielectrics206 and 208, and hard mask 210, they need not be dielectrics asdescribed in the examples herein.

Openings 212 (e.g., holes or slots) are then formed by patterning hardmask 210 and forming openings 212 through hard mask 210 and throughdielectrics 206, 208, and 204, stopping on or within semiconductor 202.For example, a mask (not shown), e.g., of photoresist, may be formedover hard mask 210 and patterned for exposing portions of hard mask 210and the dielectrics 206, 208, and 204. The exposed portions of hard mask210 and the dielectrics 206, 208, and 204 are then removed, such as byetching, e.g., using an etch that is selective to dielectrics 206, 208,and 204.

A semiconductor 214, such as polysilicon, is then formed in openings 212so as to line or fill openings 212, as shown in FIGS. 2A and 3A, e.g.,after the mask is removed. For example, semiconductor 214 may be formedby a conformal deposition process, such as chemical vapor deposition(CVD), atomic layer deposition (ALD), etc. Semiconductor 214 may extendover the upper surface of hard mask 210 for some embodiments.

In embodiments where openings 212 are only lined with the semiconductor214, a dielectric 216, such as an oxide, e.g., silicon oxide, anoxynitride, e.g., silicon oxynitride, etc., is then formed adjacent tosemiconductor 214 so as to fill the remainder of each opening 212. Forexample, dielectric 216 may be added to openings 212 until dielectric216 fills each opening 212 to a level above the upper surface ofsemiconductor 214 so that dielectric 216 extends over the upper surfaceof semiconductor 214 that may extend over the upper surface of hard mask210. In embodiments where openings 212 are filled with semiconductor214, dielectric 216 is omitted, i.e., the dielectric 216 in FIGS. 2A and3A is replaced by semiconductor 214.

Dielectric 216 may then be removed from the upper surface ofsemiconductor 214, e.g., by chemical mechanical planarization (CMP) sothat the upper surface of the dielectric 216 in each of openings 212 issubstantially flush (e.g., flush) with the upper surface ofsemiconductor 214. Upper surfaces of the dielectrics 216 may then berecessed below the upper surface of semiconductor 214 that is over theupper surface of hard mask 210 (not shown) and the upper surface of hardmask 210, as shown in FIG. 2A, e.g., using a dry or wet etch-backprocess that is selective to dielectric 216.

A semiconductor 220, e.g., polysilicon, may then be formed over therecessed upper surfaces of dielectrics 216 and the upper surface ofsemiconductor 214 that is over the upper surface of hard mask 210.Subsequently, semiconductor 220 and semiconductor 214 are removed, e.g.,by chemical mechanical planarization (CMP), stopping on hard mask 210,so that an upper surface of semiconductor 220 and the upper ends of thesubstantially vertical (e.g., vertical) sides (e.g., sidewalls) ofsemiconductor 214 are substantially flush (e.g., flush) with the uppersurface of hard mask 210, as shown in FIG. 2A.

Dielectric 216 forms a substantially vertical (e.g., vertical)dielectric pillar 235. A semiconductor that includes semiconductors 214and 220 surrounds each pillar 235. That is, each pillar 235 issurrounded by semiconductor 214 on its bottom and its substantiallyvertical (e.g., vertical) sides (e.g., sidewalls) and semiconductor 220on its top (FIGS. 2A and 3A). For example, semiconductors 214 may be indirect contact with the sidewalls of a respective pillar 235, andsemiconductor 220 may be in direct contact with the top of therespective pillar 235 and the upper portion of the sidewalls ofsemiconductor 214.

The structure of FIGS. 2A and 3A may then be patterned to form thestructure of FIGS. 2B and 3B, where FIG. 2B is a cross-section(cross-hatching omitted) of memory array 200 taken along line 2B-2B ofFIG. 3B that is a cross-section (cross-hatching omitted) taken alongline 3B-3B of FIG. 2B. For example, a mask (not shown), e.g., ofphotoresist, may be formed over the structure of FIGS. 2A and 3A andpatterned for exposing portions of hard mask 210 and the dielectrics 206and 208 under those exposed portions of hard mask 210 and a portion ofsemiconductor 220 and portions of semiconductor 214, e.g., portions ofthe substantially vertical (e.g., vertical) sidewalls of semiconductor214.

The exposed portions of hard mask 210 and the dielectrics 206 and 208are then removed, such as by etching, stopping on dielectric 204. Forexample, dielectric 204 may be a different material than dielectrics 206and 208 and hard mask 210, and the etch may be selective to dielectrics206 and 208 and hard mask 210. Alternatively, dielectrics 206, 208, and204 and hard mask 210 may be of the same material in which case an etchselective thereto would remove exposed portions of dielectric 204,stopping on or within semiconductor 202.

Subsequently, the exposed portion of semiconductor 220 (FIG. 2B) andportions of semiconductor 214, e.g., portions of the substantiallyvertical (e.g., vertical) sidewalls of semiconductor 214 (FIGS. 2B and3B), are removed using an etch selective to semiconductors 214 and 220(e.g., selective to polysilicon), stopping on or within dielectrics 204and 216. For example, the removal of the portion of semiconductor 220stops on or within dielectric 216, and the removal of the portions ofthe substantially vertical sidewalls of semiconductor 214 stops on orwithin dielectric 204. The etch that removes the portion ofsemiconductor 220 and the portions of semiconductor 214 may have adifferent chemistry than and may be performed in situ with the etch thatremoves portions of hard mask 210 and the dielectrics 206 and 208.

The removal of the portions of the substantially vertical (e.g.,vertical) sidewalls of semiconductor 214 exposes portions 230 of thesubstantially vertical (e.g., vertical) sidewalls of each pillar 235, asshown in FIG. 3B, and the removal of the exposed portion ofsemiconductor 220 exposes a portion of an upper surface 232 of eachpillar 235, as shown in FIGS. 2B and 3B. Note that portions ofsacrificial dielectrics 206, portions of dielectrics 204 and 208, andportions of hard mask 210 remain adjacent to (e.g., on) the sidewalls ofsemiconductor 214, i.e., adjacent to the substantially vertical (e.g.,vertical) sidewalls of semiconductor 214.

Removal of semiconductor 214 from the portions 230 of the substantiallyvertical (e.g., vertical) sidewall of each pillar 235 forms twoseparated opposing, substantially vertical (e.g., vertical), adjacentsemiconductor structures 255 ₁ and 255 ₂ adjacent to (e.g., on) theremainder of the substantially vertical (e.g., vertical) sidewalls ofeach pillar 235 from semiconductor 214, as shown in FIGS. 2B and 3B. Forexample, separated semiconductor structures 255 ₁ and 255 ₂ mayrespectively wrap around opposing portions of the sidewall of eachpillar 235, as shown in FIG. 3B.

Semiconductor structures 255 ₁ and 255 ₂ may remain connected togetherby the bottom of semiconductor 214, located under a respective pillar235, as shown in FIG. 2B. The ends of each semiconductor structure 255may be intersected by a single plane, as shown in FIG. 3B, e.g., theends may be about 180 degrees apart. Note that portions of semiconductor220 that are separated by the removal of the portion thereof arerespectively electrically coupled to (e.g. by direct physical contactwith) semiconductor structures 255 ₁ and 255 ₂, as shown in FIGS. 2B and3B.

In embodiments where openings 212 are filled with semiconductor 214 andthe dielectric 216 is replaced by semiconductor 214, the portion ofdielectric 216, now, semiconductor 214, spanning the space between hardmasks 210 is removed. In these embodiments, semiconductor structures 255₁ and 255 ₂ are semiconductor pillars. For example, the portions 231 inFIG. 3C are semiconductor 214 and form portions of semiconductorstructures 255 ₁ and 255 ₂. In addition the portion located between theportions 231 is an opening (e.g., that may later be filled with adielectric) that enables, for example, a charge trap 260, e.g., acontinuous charge trap 260, to be formed adjacent to and around thesemiconductor structures 255 ₁ and 255 ₂.

Sacrificial dielectrics 206 are then removed from dielectrics 204 and208 and semiconductor structures 255 ₁ and 255 ₂, and sacrificial hardmask 210 is removed from a dielectric 208, e.g., using an etch selectiveto dielectrics 206 (e.g., and etch that is selective to nitride). Thisexposes dielectrics 204 and 208 and semiconductor structures 255 ₁ and255 ₂. Then, a plurality of charge storage structures, such as thoseforming a continuous charge trap 260, are formed substantiallyconcurrently (e.g., concurrently) adjacent to the dielectrics 204 and208, semiconductor structures 255 ₁ and 255 ₂, and portions 230 of thesubstantially vertical (e.g., vertical) sidewalls of each pillar 235, asshown in FIGS. 2C and 3C, where FIG. 2C is a cross-section(cross-hatching omitted) of memory array 200 taken along line 2C-2C ofFIG. 3C that is a cross-section (cross-hatching omitted) taken alongline 3C-3C of FIG. 2C. For example, charge trap 260 may be formed by aconformal deposition process, such as chemical vapor deposition (CVD),atomic layer deposition (ALD), etc. Alternatively, charge trap 260 maybe grown.

For some embodiments, charge trap 260 may include a tunnel dielectric,such as a tunnel oxide, formed adjacent to the dielectrics 204 and 208,semiconductor structures 255 ₁ and 255 ₂, and portions 230 of thesubstantially vertical (e.g., vertical) sidewalls of each pillar 235,charge trapping material, such as a nitride, formed adjacent to (e.g.,on) the tunnel dielectric, and a blocking dielectric, such as a blockingoxide, formed adjacent to (e.g., on) the charge trapping material. Forother embodiments, charge trap 260 may be a dielectric, e.g., ahigh-dielectric constant (high-K) dielectric, such as alumina (Al₂O₃)having a K of about 10, with embedded conductive particles (e.g.,nano-dots), such as embedded metal particles or embedded nano-crystals(e.g., silicon, germanium, or metal crystals), a silicon richdielectric, or SiON/Si₃N₄.

A conductor, e.g., a metal, such as tungsten, tantalum nitride, titaniumnitride, tungsten nitride, etc., is formed adjacent to the structure ofFIGS. 2C and 3C, e.g., using a conformal deposition process, such aschemical vapor deposition (CVD), atomic layer deposition (ALD), etc. Ingeneral, the conductor, may comprise, consist of, or consist essentiallyof conductively doped polysilicon and/or may comprise, consist of, orconsist essentially of metal, such as a refractory metal, or ametal-containing material, such as a refractory metal silicide layer, aswell as any other conductive material. The metals of chromium (Cr),cobalt (Co), hafnium (Hf), molybdenum (Mo), niobium (Nb), tantalum (Ta),titanium (Ti), tungsten (W), vanadium (V) and zirconium (Zr) aregenerally recognized as refractory metals.

An etch-back, e.g., an anisotropic etch-back, is then performed toremove excess conductor to form control gates 265 from the remainingconductor, as shown in FIGS. 2D and 3D, where FIG. 2D is a cross-section(cross-hatching omitted) of memory array 200 taken along line 2D-2D ofFIG. 3D that is a cross-section (cross-hatching omitted) taken alongline 3D-3D of FIG. 2D.

Control gates 265 _(1,1) and 265 _(1,2) are respectively control gatesof select gates, such as source select gates 270 ₁ and 270 ₂; controlgates 265 _(2,1) and 265 _(2,2) are respectively control gates of memorycells (e.g., non-volatile memory cells) 272 ₁ and 272 ₂; and controlgates 265 _(3,1) and 265 _(3,2) are respectively control gates of selectgates, such as s drain select gates 274 ₁ and 274 ₂, as shown in FIGS.2D and 3D. Control gates 265 _(2,1) and 265 _(2,2) may respectively formportions of access lines (e.g., word lines) 280 ₁ and 280 ₂, as shown inFIG. 3D. For example, control gates 265 _(2,1) and 265 _(2,2) may berespectively coupled to word lines 280 ₁ and 280 ₂. Similarly, controlgates 265 _(1,1) and 265 _(1,2) respectively form portions of sourceselect lines and control gates 265 _(3,1) and 265 _(3,2) respectivelyform portions of drain select lines. For example, control gates 265_(1,1) and 265 _(1,2) may be respectively coupled to the source selectlines, and control gates 265 _(3,1) and 265 _(3,2) may be respectivelycoupled to the drain select lines.

Note that a memory cell 272 is located at each intersection of a wordline 280 and charge trap 260; a source select gate 270 is located ateach intersection of a source select line and charge trap 260; and drainselect gate 274 located at each intersection of a drain select line andcharge trap 260. Also note that a word line 280 ₁ is commonly coupled tothe memory cells 272 ₁ respectively on different pillars 235, and a wordline 280 ₂ is commonly coupled to the memory cells 272 ₂ respectively onthose different pillars 235, as shown in FIG. 3D.

A portion of charge trap 260 and a dielectric 208 thereunder and on asidewall of semiconductor structure 255 ₁ are interposed betweensuccessive control gates 265 _(2,1) of successive memory cells 272 ₁ ofa string of memory cells 272 ₁ and thus electrically isolate successivecontrol gates 265 ₁ of a string of memory cells 272 ₁ from each other,as shown in FIG. 2D. A portion of charge trap 260 and a dielectric 208thereunder and on a sidewall of semiconductor structure 255 ₂ areinterposed between successive control gates 265 _(2,2) of successivememory cells 272 ₂ of a string of memory cells 272 ₂ and thuselectrically isolate successive control gates 265 ₂ of a string ofmemory cells 272 ₂ from each other, as shown in FIG. 2D.

A portion of charge trap 260 and a dielectric 208 adjacent thereto andadjacent to a sidewall of semiconductor structure 255 ₁ are interposedbetween the control gate 265 _(1,1) of a source select gate 270 ₁ andthe control gate 265 _(2,1) of a memory cell 272 ₁ at one end of thestring of memory cells 272 ₁, electrically isolating those controlgates, and between the control gate 265 _(3,1) of a drain select gate274 ₁ and the control gate 265 _(2,1) of the memory cell 272 ₁ at theopposite end of the string of memory cells 272 ₁, electrically isolatingthose control gates, as shown in FIG. 2D. A portion of charge trap 260and a dielectric 208 adjacent thereto and adjacent to a sidewall ofsemiconductor structure 255 ₂ are interposed between the control gate265 _(1,2) of a source select gate 270 ₂ and the control gate 265 _(2,2)of a memory cell 272 ₂ at one end of the string of memory cells 272 ₂,electrically isolating those control gates, and between the control gate265 _(3,2) of a drain select gate 274 ₂ and the control gate 265 _(2,2)of the memory cell 272 ₂ at the opposite end of the string of memorycells 272 ₂, electrically isolating those control gates. Note thatportions of charge trap 260 are interposed between the sidewalls ofsemiconductor structures 255 ₁ and 255 ₂ and the control gates 265,electrically isolating the semiconductor structures 255 ₁ and 255 ₂ fromcontrol gates 265, as shown in FIGS. 2D and 3D.

For some embodiments, after the etch-back that forms the control gates,a portion of the charge trap 260, a dielectric 208, and a portion ofdielectric 204 may be optionally removed, e.g., using a etch selectiveto the charge trap 260, dielectric 208, and dielectric 204. Removal ofthe portion of the charge trap 260 exposes a portion of the uppersurface 232 of each of the pillars 235, portions of the semiconductor220 over each of the pillars 235, the upper ends of semiconductorstructures 255, portions of the sidewalls of semiconductor structures255 adjacent their upper ends, and an upper surface of each of thecontrol gates 265 _(3,1) and 265 _(3,2), as shown in FIG. 2D. Thedielectric 208 is also removed from the portions of the sidewalls ofsemiconductor structures 255 adjacent their upper ends. Removal of theportion of dielectric 204 exposes portions of an upper surface ofsemiconductor 202.

Source/drain regions 275 (e.g., drains) may then be formed (e.g.implanted) in the exposed semiconductors 220 and the exposed portions ofthe sidewalls of semiconductor structures 255 adjacent their upper ends,as shown in FIG. 2D. Source/drain regions 277 (e.g., source lines) maybe formed (e.g. implanted), e.g. substantially concurrently (e.g.,concurrently) with source/drain regions 275, in the exposed portions ofsemiconductor 202. For example, source/drain regions 275 and 277 may ben-type when semiconductor 202 is p-type and p-type when semiconductor202 is n-type. Source/drain regions 277 are electrically coupled tosource select gates 270 ₁ and 270 ₂ by semiconductor structures 255.

For other embodiments, source/drain regions, such as source/drainregions 277, may be implanted in semiconductor 202 through openings 212(FIG. 2A), e.g., using hard mask 210 as a mask or using the mask overhard mask 210 in the event that the mask is not yet removed.Alternatively, for some embodiments, a contiguous source/drain region(e.g., a plane) located under the openings 212 and dielectric 204 mayreplace source/drain regions 277 and may be implanted in semiconductor202 before forming dielectric 204. For example, contiguous source/drainregion may electrically coupled to source select gates 270 ₁ and 270 ₂by semiconductor structures 255.

A dielectric (not shown), such as bulk insulation, may then be formedover the structure in FIG. 2D so that source/drain regions 275 and 277are covered thereby. Openings may then be formed within the dielectricto expose source/drain regions 275. Contacts (not shown) may then beformed within the openings, e.g., so that a contact is in contact witheach source/drain region. 275.

One example for the dielectric would be a doped silicate glass. Examplesof doped silicate glasses include BSG (borosilicate glass), PSG(phosphosilicate glass), and BPSG (borophosphosilicate glass). Anotherexample for the dielectric would be TEOS (tetraethylorthosilicate). Thecontacts may comprise, consist of, or consist essentially of a metal ormetal-containing layer and may be aluminum, copper, a refractory metal,or a refractory metal silicide layer. In some embodiments, the conductormay contain multiple metal-containing layers, e.g., a titanium nitride(TiN) barrier layer formed over (e.g., in direct physical contact with)a source/drain region 275, a titanium (Ti) adhesion layer formed overthe barrier layer, and a tungsten (W) layer formed over the adhesionlayer.

A conductor (not shown) that may be metal, such as aluminum, may then beformed over the dielectric formed over the structure of FIG. 2D. Theconductor is patterned, etched, and processed, e.g., using standardprocessing, to produce individual data lines, such as bit lines, thatare electrically connected to the contacts, and thus the source/drainregions 275 and drain select gates 274 ₁ and 274 ₂.

Semiconductor structures 255, and 255 ₂ respectively form channelregions of memory cells 272, and 272 ₂ and respectively electricallycouple memory cells 272, and 272 ₂ in series to form strings (e.g., NANDstrings) of memory cells 272, and 272 ₂. In other words, duringoperation of a string of memory cells 272 ₁, a channel(s) can be formedin a semiconductor structure 255 ₁, and during operation of a string ofmemory cells 272 ₂, a channel(s) can be formed in a semiconductorstructure 255 ₂. Semiconductor structure 255, electrically couples astring of memory cells 272, in series to a source select gate 270, atone end of that string and a drain select gate 274, in series to theopposite end of that string, and semiconductor structure 255 ₂electrically couples a string of memory cells 272 ₂ in series to asource select gate 270 ₂ at one end of that string and a drain selectgate 274, in series to the opposite end of that string, as shown in FIG.2D.

A string of memory cells 272, and the source select gate 270, and thedrain select gate 274 ₁ coupled to the ends thereof are located adjacentto the same portion of the sidewall (e.g., the same side) of arespective pillar 235, and a string of memory cells 272 ₂ and the sourceselect gate 270 ₂ and the drain select gate 274 ₂ coupled to the endsthereof are located adjacent to the same opposite portion of thesidewall (e.g., the same opposite side) of a respective pillar 235. Inaddition, the word lines 280, coupled to memory cells 272, are coupledto the same portion of the sidewall (e.g., the same side) of charge trap260, and the word lines 280 ₂ coupled to memory cells 272 ₂ are coupledto the same opposite portion of the sidewall (e.g., the same oppositeside) of charge trap 260.

A source select gate 270, and a drain select gate 274, and the string ofmemory cells 272, electrically coupled thereto are formed adjacent to afirst portion of the substantially vertical (e.g., vertical) sidewalleach pillar 235. A source select gate 270 ₂ and a drain select gate 274₂ and the string of memory cells 272 ₂ electrically coupled thereto areformed adjacent to a second portion of the substantially vertical (e.g.,vertical) sidewall the respective pillar 235, as shown in FIGS. 2D and3D. That is, there are two strings of memory cells on each pillar 235.

Each memory cell 272 ₁ includes a portion of semiconductor structure 255₁, as a channel region thereof, adjacent to (e.g., in direct contactwith) an outer surface of the first portion of the sidewall of arespective pillar 235, a portion of a charge trap 260 adjacent to theportion of semiconductor structure 255 ₁, and a control gate 265 _(2,1)adjacent to the portion of charge trap 260, as shown in FIGS. 2D and 3D.Each memory cell 272 ₂ includes a portion of semiconductor structure 255₂, as a channel region thereof adjacent to (e.g., in direct contactwith) an outer surface of the second portion of the sidewall of therespective pillar 235, an other portion of the charge trap 260 adjacentto the portion of the semiconductor structure 255 ₂, and a control gate265 _(2,2) adjacent to the other portion of the charge trap 260, asshown in FIGS. 2D and 3D.

The control gates 265 _(2,1) and 265 _(2,2) respectively of memory cells272 ₁ and 272 ₂ are formed adjacent to opposing portions of charge trap260, e.g., the portions that respectively wrap around opposing portionsof the sidewall of each pillar 235. For example, two memory cells, suchas memory cells 272 ₁ and 272 ₂, may respectively wrap around opposingportions of the sidewall of each pillar 235, e.g., and as such, may betermed “half-wrap” memory cells. Control gates 265 _(2,1) and 265 _(2,2)may be electrically isolated from each other, e.g., by a dielectric (notshown), e.g., bulk insulation, that may be formed between control gates265 _(2,1) and 265 _(2,2), and thus the word lines 280 ₁ and 280 ₂.Adjacent word lines 280 ₂ may be similarly electrically isolated fromeach other.

For some embodiments, charge trap 260 may form a contiguous structurethat is wrapped completely around the periphery of a respective pillar235, including the semiconductor structures 255 ₁ and 255 ₂. Forexample, the portions of charge trap 260 respectively adjacent tosemiconductor structures 255 ₁ and 255 ₂ may be contiguous. Portions ofthe charge trap 260 may be interposed between a semiconductor structure255 ₁ and a semiconductor structure 255 ₂. For example, the portions ofcharge trap 260 interposed between a semiconductor structure 255 ₁ and asemiconductor structure 255 ₂ may be respectively in direct contact withopposing portions 230 of the sidewall of the respective pillar 235, asshown in FIG. 3D.

For other embodiments, a portion of the charge traps 260 located betweenword lines 280 ₁ and 280 ₂ may be removed, e.g., using an isotropicetch, after forming the individual word lines 280 ₁ and 280 ₂. Thisseparates a charge trap 260 into separated first and second portionsrespectively adjacent to semiconductor structures 255 ₁ and 255 ₂.

For example, in embodiments where semiconductor fills openings 212,dielectric 216, and thus dielectric pillars 235, is omitted, andstructures 255 ₁ and 255 ₂ are semiconductor pillars that includesemiconductor portions 231, as shown in FIGS. 3C and 3D, the separatedfirst and second portions of the charge trap 260 may wrap (e.g.,completely) around the structures 255 ₁ and 255 ₂, as indicated bydashed lines 291 in FIG. 3D, with the portion of charge trap 260 anddielectric pillar 235 between dashed lines 291 being omitted.

Source select gates 270 ₁ and 270 ₂ and drain select gates 274 ₁ and 274₂ have substantially the same (e.g., the same) cross-sections as thoseshown for memory cells 272 in FIG. 3D. For example, a source select gate270 ₁ may include a portion of semiconductor structure 255 ₁, as achannel region thereof, adjacent to the first portion of the sidewall ofa respective pillar 235, a portion of a charge trap 260 adjacent to theportion of semiconductor structure 255 ₁, and a control gate 265 _(1,1)adjacent to the portion of charge trap 260, as shown in FIG. 2D. Asource select gate 270 ₂ may include a portion of a semiconductorstructure 255 ₂, as a channel region thereof, adjacent to the secondportion of the sidewall of a respective pillar 235, a portion of acharge trap 260 adjacent to the portion of semiconductor structure 255₂, and a control gate 265 _(1,2) adjacent to the portion of charge trap260, as shown in FIG. 2D. A drain select gate 274 ₁ may include a otherportion of semiconductor structure 255 ₁, as a channel region thereof,adjacent to the first portion of the sidewall of a respective pillar235, an other portion of a charge trap 260 adjacent to the other portionof semiconductor structure 255 ₁, and an other portion control gate 265_(3,1) adjacent to the other portion of charge trap 260, as shown inFIG. 2D. A drain select gate 274 ₂ may include an other portion ofsemiconductor structure 255 ₂, as a channel region thereof, adjacent tothe second portion of the sidewall of a respective pillar 235, an otherportion of charge trap 260 adjacent to the other portion ofsemiconductor structure 255 ₂, and a control gate 265 _(3,2) adjacent tothe other portion of charge trap 260, as shown in FIG. 2D. The sourceand drain select gates can be programmable, i.e., capable of alteringtheir threshold voltages, and may be programmed or left unprogrammed.

FIGS. 4A-4E and 5A-5E are cross-sectional views of a portion of a memoryarray 400, during various stages of fabrication, according to otherembodiments. Memory array 400 may form a portion of memory array 104 ofFIG. 1. Common numbering is used in FIGS. 4A-4E and 5A-5E and in FIGS.2A-2D and 3A-3D to denote similar (e.g., the same) components.

FIG. 4A is a cross-section (cross-hatching omitted) of memory array 400taken along line 4A-4A of FIG. 5A that is a cross-section(cross-hatching omitted) taken along line 5A-5A of FIG. 4A. Theformation of the structure of FIGS. 4A and 5A may be substantially thesame as the formation of the structure of FIGS. 2A and 3A, as describedabove.

Openings 412 may be formed, e.g., as described above in conjunction withFIGS. 2A and 3A for openings 212, except that the shape of thecross-sections of openings 412 in FIG. 5A differs from the shape of thecross-sections openings 212 in FIG. 3A. Semiconductor 214 is formed inopenings 412 so as to line or fill openings 412, e.g., as describedabove in conjunction with FIGS. 2A and 3A for openings 212, except thatthe shape of the cross-sections of semiconductor 214 in FIG. 5A differsfrom the shape of the cross-sections of semiconductor 214 in FIG. 3A. Inembodiments where openings 412 are only lined with the semiconductor214, substantially vertical (e.g., vertical) dielectric pillarstructures 435 are formed within openings 212 from dielectric 216, e.g.,as described above in conjunction with FIGS. 2A and 3A for pillars 235,except the shape of the cross-sections of pillar structures 435 in FIG.5A differs from the shape of the cross-sections pillars 235 in FIG. 3A.

FIG. 4B is a cross-section (cross-hatching omitted) of memory array 400taken along line 4B-4B of FIG. 5B that is a cross-section(cross-hatching omitted) taken along line 5B-5B of FIG. 4B. Theformation of the structure of FIGS. 4B and 5B may be substantially thesame as the formation of the structure of FIGS. 2B and 3B, as describedabove. For example, a mask (not shown), e.g., of photoresist, may beformed over the structure of FIG. 4A and patterned for exposing portionsof hard mask 210 and the dielectrics 206 and 208 under those exposedportions of hard mask 210, a portion of semiconductor 220, and portionsof semiconductor 214, e.g., portions of the substantially vertical(e.g., vertical) sidewalls of semiconductor 214.

The exposed portions of hard mask 210 and the dielectrics 206 and 208are then removed, e.g., as described above in conjunction with FIGS. 2Band 3B. Subsequently, the exposed portion of semiconductor 220 (FIG. 4B)and portions of semiconductor 214, e.g., portions of the substantiallyvertical (e.g., vertical) sidewalls of semiconductor 214 (FIG. 5B), areremoved, e.g., as described above in conjunction with FIGS. 2B and 3B,stopping on or within dielectrics 204 and 216. For example, the removalof the portion of semiconductor 220 stops on or within dielectric 216and the removal of the portions of the substantially vertical sidewallsof semiconductor 214 stops on or within dielectric 204. The etch thatremoves the portion of semiconductor 220 and the portions ofsemiconductor 214 may have a different chemistry than and may beperformed in situ with the etch that removes portions of hard mask 210and the dielectrics 206 and 208.

The removal of the portions of the substantially vertical (e.g.,vertical) sidewalls of semiconductor 214 exposes portions 430 of thesubstantially vertical (e.g., vertical) sidewalls of each pillarstructure 435, as shown in FIG. 5B, and removal of the portion ofsemiconductor 220 exposes a portion of an upper surface 432 of eachpillar structure 435, as shown in FIGS. 4B and 5B. Note that portions ofsacrificial dielectrics 206, portions of dielectrics 204 and 208, andportions of hard mask 210 remain adjacent to (e.g., on) the sidewalls ofsemiconductor 214, i.e., adjacent to the substantially vertical (e.g.,vertical) sidewalls of semiconductor 214.

Removal of semiconductor 214 from the portions 430 of the substantiallyvertical (e.g., vertical) sidewalls of each pillar structure 435 formstwo separated opposing, substantially vertical (e.g., vertical) adjacentsemiconductor structures 414 ₁ and 414 ₂ adjacent to (e.g., on) theremainder of the substantially vertical (e.g., vertical) sidewalls ofeach pillar structure 435 from semiconductor 214, as shown in FIGS. 4Band 5B. For example, opposing portions 430 of the sidewall of a pillarstructure 435 are interposed between and separate semiconductorstructures 414 ₁ and 414 ₂ from each other. Note that portions ofsemiconductor 220 that are separated by the removal of the portionthereof are respectively electrically coupled (e.g. by direct physicalcontact with) to semiconductor structures 414 ₁ and 414 ₂, as shown inFIGS. 4B and 5B.

The structure of FIGS. 4B and 5B may then be patterned to form thestructure of FIGS. 4C and 5C, where FIG. 4C is a cross-section(cross-hatching omitted) of memory array 400 taken along line 4C-4C ofFIG. 5C that is a cross-section (cross-hatching omitted) taken alongline 5C-5C of FIG. 4C. For example, a mask (not shown), e.g., ofphotoresist, may formed over the structure of FIGS. 4B and 5B andpatterned for forming openings 440, e.g., for removal of a portion ofsemiconductor structures 414 ₁ and 414 ₂, a portion of semiconductor 220over each pillar, and a portion of each pillar structure 435. Forexample, an opening 440 is formed through dielectric 216 and extendsthrough semiconductor structures 414 ₁ and 414 ₂, as shown in FIG. 5C.

A portion each semiconductor 220 over a pillar structure 435 and aportion of each of semiconductor structures 414 ₁ and 414 ₂ that extendsabove the upper surface 432 of each pillar structure 435 patterned forremoval are then removed, such as by etching (e.g., using an etch thatis selective to polysilicon), stopping on or within a respective pillarstructure 435, thereby forming an upper portion of a respective opening440. Subsequently, a remaining portion of each of semiconductorstructures 414 ₁ and 414 ₂ patterned for removal and a portion of eachpillar is removed, such as by etching (e.g., using an etch chemistrydifferent than that used for forming upper portion of a respectiveopening 440), stopping on or within semiconductor 202, thereby formingthe remainder of each opening 440.

The formation of each opening 440 forms two separate pillars 445 ₁ and445 ₂ from each pillar structure 435, as shown in FIG. 5C. The formationof each opening 440 also forms a semiconductor structure 455 ₁ and asemiconductor structure 455 ₂ from each semiconductor structure 414 ₁that are separated from each other and a semiconductor structure 455 ₁and a semiconductor structure 455 ₂ from each semiconductor structure414 ₂ that are separated from each other. Semiconductor structures 455 ₁are respectively adjacent to (e.g., on) opposing portions of thesidewall (e.g., opposite corners) of each pillar 445 ₁ and are separatedfrom each other, as shown in FIG. 5C. Semiconductor structures 455 ₂ arerespectively adjacent to (e.g., on) opposing portions (e.g., oppositecorners) of the sidewall each pillar 445 ₂ and are separated from eachother, as further shown in FIG. 5C. This means that there aresemiconductor structures 455 ₁ respectively on opposite corners of eachof pillars 445 ₁, and there are semiconductor structures 455 ₂respectively on opposite corners of each of pillars 445 ₂.

For example, the combination of the removal of semiconductor 214 fromthe portion 430 of the sidewall of each pillar structure 435 (FIG. 5B)and the formation of each opening 440 (FIG. 5C) forms four separateconductors from the semiconductor 214 on each pillar structure 435. Notethat semiconductor structures 455 ₂ and 455 ₂ may remain connectedtogether by the bottom of semiconductor 214, located under a respectivepillar 455 ₂, as shown in FIG. 4B. Similarly, semiconductor structures455 ₁ and 455 ₁ may remain connected together by the bottom ofsemiconductor 214, located under a respective pillar 455 ₁ (not shown).The ends of each semiconductor structure 455 may be respectivelyintersected by planes that are substantially perpendicular (e.g.,perpendicular) to each other, as shown in FIG. 5C, e.g., the ends may beabout 90 degrees apart.

The portion of semiconductor 220 that is coupled to semiconductorstructure 414 ₁ is cut into two parts during the formation of opening440 so that the two parts are respectively electrically coupled to(e.g., by direct physical contact with) a set of semiconductorstructures 455 ₁ and 455 ₂. The portion of semiconductor 220 that iscoupled to semiconductor structure 414 ₂ is also cut into two partsduring the formation of opening 440 so that the two parts arerespectively electrically coupled to (e.g., by direct physical contactwith) a set of semiconductor structures 455 ₁ and 455 ₂.

Each pillar 445 ₁ has a substantially vertical (e.g., vertical) sidewall443 ₁, and each pillar 445 ₂ has a substantially vertical (e.g.,vertical) sidewall 443 ₂, as shown in FIGS. 4C and 5C. Each sidewall 443₁ has an exposed substantially vertical (e.g., vertical) portion 442 ₁and an exposed substantially vertical (e.g., vertical) portion 447 ₁that is the same as an exposed portion 430 of the single pillarstructure 435. Remaining portions of each sidewall 443 ₁, e.g., otherthan portions 442 ₁ and 447 ₁, are covered by semiconductor structures455 ₁. Each sidewall 443 ₂ has an exposed substantially vertical (e.g.,vertical) portion 442 ₂ and an exposed substantially vertical (e.g.,vertical) portion 447 ₂ that is the same as another exposed portion 430of the single pillar structure 435. Remaining portions of each sidewall443 ₂, e.g., other than portions 442 ₂ and 447 ₂, are covered bysemiconductor structures 455 ₂. Note that the exposed portions 442 and447 may face in opposite directions.

Note that the cross-section taken along line 4B-4B in FIG. 5C and shownin FIG. 4B is substantially unaffected (e.g., unaffected) by theformation of openings 440. That is, the cross-section taken along line4B-4B in FIG. 5B before the formation of openings 440 and thecross-section taken along line 4B-4B in FIG. 5C after the formation ofopenings 440 remains substantially the same (e.g., the same), as isapparent from using FIG. 4B to correspond to both the cross-sectionstaken along lines 4B-4B in FIGS. 5B and 5C.

FIG. 4D is a cross-section (cross-hatching omitted) of memory array 400taken along line 4D-4D of FIG. 5D that is a cross-section(cross-hatching omitted) taken along line 5D-5D of FIG. 4D. Theformation of the structure of FIGS. 4D and 5D may be substantially thesame as the formation of the structure of FIGS. 2C and 3C, as describedabove. For example, sacrificial dielectrics 206 are then removed fromdielectrics 204 and 208 and semiconductor structures 455 ₁ and 455 ₂,and sacrificial hard mask 210 is removed from a dielectric 208, e.g., asdescribed above in conjunction with FIGS. 2C and 3C. This exposesdielectrics 204 and 208 and semiconductor structures 455 ₁ and 455 ₂.Then, a plurality of charge storage structures, such as those forming acontinuous charge trap 260, is formed substantially concurrently (e.g.,concurrently) adjacent to the dielectrics 204 and 208, semiconductorstructures 455 ₁ and 455 ₂, and portions 442 and 447 of thesubstantially vertical (e.g., vertical) sidewalls 443 of each pillar445, as shown in FIGS. 4D and 5D, e.g., as described above inconjunction with FIGS. 2C and 3C.

FIG. 4E is a cross-section (cross-hatching omitted) of memory array 400taken along line 4E-4E of FIG. 5E that is a cross-section(cross-hatching omitted) taken along line 5E-5E of FIG. 4E. Theformation of the structure of FIGS. 4E and 5E may be substantially thesame as the formation of the structure of FIGS. 2D and 3D, as describedabove. For example, control gates 465 are formed from a conductor, e.g.,as described above in conjunction with FIGS. 2D and 3D for control gates265.

For example, control gates 465 _(1,1) and 465 _(1,2) are respectivelycontrol gates of select gates, such as source select gates 470 _(2,1)and 470 _(2,2); control gates 465 _(2,1) and 465 _(2,2) are respectivelycontrol gates of memory cells (e.g., non-volatile memory cells) 472_(2,1) and 472 _(2,2); and control gates 465 _(3,1) and 465 _(3,2) arerespectively control gates of select gates, such as drain select gates474 _(2,1) and 474 _(2,2), as shown in FIGS. 4E and 5E. Control gates465 _(2,1) and 465 _(2,2) may respectively form portions of access lines(e.g., word lines 480 ₁ and 480 ₂) as shown in FIG. 5E. For example,control gates 465 _(2,1) and 465 _(2,2) may be respectively coupled toword lines 480 ₁ and 480 ₂. Similarly, control gates 465 _(1,1) and 465_(1,2) respectively form portions of source select lines and controlgates 465 _(3,1) and 465 _(3,2) respectively form portions of drainselect lines. For example, control gates 465 _(1,1) and 465 _(1,2) maybe respectively coupled to the source select lines and control gates 465_(3,1) and 465 _(3,2) may be respectively coupled to the drain selectlines. Note that a memory cell 472 is located at each intersection of aword line 480 and charge trap 260; a source select gate 470 is locatedat each intersection of a source select line and charge trap 260; anddrain select gate 474 located at each intersection of a drain selectline and charge trap 260.

After forming control gates 465, a portion of the charge trap 260, adielectric 208, and a portion of dielectric 204 may be optionallyremoved, e.g., as described above in conjunction with FIGS. 2D and 3D,exposing a portion of an upper surface of each of the pillar structures435, portions of the semiconductor 220 adjacent to each of the pillars235, the upper ends of semiconductor structures 455, portions of thesidewalls of semiconductor structures 455 adjacent their upper ends, andan upper surface of each of the control gates 465 _(3,1) and 465 _(3,2),as shown in FIG. 4E.

Source/drain regions 275 (e.g., drains) may then be formed (e.g.implanted) in the exposed semiconductors 220 and the exposed portions ofthe sidewalls of semiconductor structures 455 adjacent their upper ends,as shown in FIG. 4E, e.g., as described above in conjunction with FIG.2D. Source/drain regions 277 (e.g., source lines) may be formed (e.g.implanted), e.g. substantially concurrently (e.g., concurrently) withsource/drain regions 275 in the exposed portions of semiconductor 202,e.g., as described above in conjunction with FIG. 2D. Data lines (notshown), such as bit lines, may be electrically coupled to source/drainregions 275, and thus the drain select gates 474 _(2,1) and 274 _(2,2),by contacts, e.g., as described above in conjunction with FIG. 2D.Source/drain regions 277 are electrically coupled to source select gates470 _(2,1) and 470 _(2,2) by semiconductor structures 455 ₂.

The two semiconductor structures 455 ₂ formed adjacent to (e.g. on) eachof pillars 445 ₂ respectively form channel regions of memory cells 472_(2,1) and 472 _(2,2) and electrically couple memory cells 472 _(2,1)and 472 _(2,2) in series to form strings (e.g., NAND strings) of memorycells 472 _(2,1) and 472 _(2,2). In other words during operation of astring of memory cells 472 _(2,1), a channel(s) can be formed in therespective semiconductor structure 455 ₂, and during operation of astring of memory cells 472 _(2,2), a channel(s) can be formed in therespective semiconductor structure 455 ₂. One of the semiconductorstructures 455 ₂ electrically couples a string of memory cells 472_(2,1) in series to a source select gate 470 _(2,1) at one end of thatstring and a drain select gate 474 _(2,1) in series to the opposite endof that string, and the other semiconductor structure 455 ₂ electricallycouples a string of memory cells 472 _(2,2) in series to a source selectgate 470 _(2,2) at one end of that string and a drain select gate 474_(2,2) in series to the opposite end of that string, as shown in FIG.4E.

A source select gate 470 _(2,1), a drain select gate 474 _(2,1), and thestring of memory cells 472 _(2,1) electrically coupled thereto areformed adjacent to a first portion of the substantially vertical (e.g.,vertical) sidewall each pillar 445 ₂, and a source select gate 470_(2,2), a drain select gate 474 _(2,2), and the string of memory cells472 _(2,2) electrically coupled thereto are formed adjacent to a secondportion of the substantially vertical (e.g., vertical) sidewall therespective pillar 445 ₂, as shown in FIGS. 4E and 5E. That is, there aretwo strings of memory cells with source and drain select gates coupledthereto adjacent to (e.g., on) each pillar 445 ₂.

There are two strings of memory cells with source and drain select gatescoupled thereto adjacent to (e.g., on) each pillar 445 ₁. For example,the two semiconductor structures 455 ₁ formed adjacent to (e.g., on)each of pillars 445 ₁ respectively form channel regions of memory cells472 _(1,1) and 472 _(1,2) (FIG. 5E) and electrically couple memory cells472 _(1,1) and 472 _(1,2) in series to form strings (e.g., NAND strings)of memory cells 472 _(1,1) and 472 _(1,2). The ends of each of thesestrings are respectively coupled to a source select gate and a drainselect gate by a respective one of the two semiconductor structures 455₁. A string of memory cells 472 _(1,1) (e.g., NAND string) coupled inseries and the source and a drain select gates respectively coupled inseries to the ends thereof are located adjacent to a first portion ofthe sidewall of a respective pillar 445 ₁, and a string of memory cells472 _(1,2) (e.g., NAND string) coupled in series and the source and adrain select gates respectively coupled in series to the ends thereofare located adjacent to a second portion of the sidewall of therespective pillar 445 ₁.

Each memory cell 472 _(1,1) includes a portion of semiconductorstructure 455 ₁, as a channel region thereof, adjacent to (e.g., indirect contact with) an outer surface of a first portion (e.g., acorner) of the sidewall 443 ₁ (FIG. 5D) of a respective pillar 445 ₁, aportion of a charge trap 260 adjacent to the portion of semiconductorstructure 455 ₁, and a control gate 465 _(2,1) adjacent to the portionof charge trap 260, as shown in FIG. 5E. Each memory cell 472 _(1,2)includes a portion of an other semiconductor structure 455 ₁, as achannel region thereof, adjacent to (e.g., in direct contact with) anouter surface of a second portion (e.g., an opposite corner) of thesidewall 443 ₁ of the respective pillar 445 ₁, an other portion of thecharge trap 260 adjacent to the portion of the other semiconductorstructure 455 ₁, and a control gate 465 _(2,2) adjacent to the otherportion of the charge trap 260, as shown in FIG. 5E. For example, amemory cell 472 _(1,1) and a memory cell 472 _(1,2) may wrap aroundportions of sidewall 443 ₁ of a pillar 445 ₁.

Each memory cell 472 _(2,1) includes a portion of semiconductorstructure 455 ₂, as a channel region thereof, adjacent to (e.g., indirect contact with) an outer surface of a first portion (e.g., acorner) of the sidewall 443 ₂ (FIG. 5D) of a respective pillar 445 ₂, aportion of a charge trap 260 adjacent to the semiconductor structure 455₂, and a control gate 465 _(2,1) adjacent to the portion of the chargetrap 260, as shown in FIGS. 4E and 5E. Each memory cell 472 _(2,2)includes a portion of an other semiconductor structure 455 ₂, as achannel region thereof, adjacent to (e.g., in direct contact with) anouter surface of a second portion (e.g., an opposite corner) of thesidewall 443 ₂ of the respective pillar 445 ₂, an other portion of thecharge trap 260 adjacent to the portion of the other semiconductorstructure 455 ₂, and a control gate 465 _(2,2) adjacent to the otherportion of the charge trap 260, as shown in FIGS. 4E and 5E. Forexample, a memory cell 472 _(2,1) and a memory cell 472 _(2,2) may wraparound portions of sidewall 443 ₂ of a pillar 445 ₂. Note that fourmemory cells, e.g., memory cells 472 _(1,1), 472 _(1,2), 472 _(2,1), and472 _(2,1), respectively wrap around the four corners of a pillarstructure 435, e.g., and as such, may be termed “quarter-wrap” memorycells.

Control gates 465 _(2,1) and 465 _(2,2), and thus the word lines 480 ₁and 480 ₂, may be electrically isolated from each other, e.g., by adielectric (not shown), e.g., bulk insulation, that may be formedbetween word lines 480 ₁ and 480 ₂. Adjacent word lines 480 ₂ may besimilarly isolated from each other.

For some embodiments, charge traps 260 may form contiguous structuresthat are wrapped completely around the peripheries of pillars 445 ₁,including the two semiconductor structures 455 ₁ adjacent thereto, andcompletely around the peripheries of pillars 445 ₂, including the twosemiconductor structures 455 ₂ adjacent thereto. A portion of a chargetrap 260 may be interposed between the two semiconductor structures 455₂ on the sidewall 443 ₂, and a portion of a charge trap 260 may beinterposed between the two semiconductor structures 455 ₁ on thesidewall 443 ₁. A dielectric, e.g., bulk insulation, may be formed in anopening 485, i.e., remaining portion of an opening 440 (FIG. 5C),located between portions of the charge traps 260 wrapped around theperipheries of pillars 445 ₁ and 445 ₂.

Portions 442 ₁ and 442 ₂ respectively of sidewalls 443 ₁ and 443 ₂respectively of pillars 445 ₁ and 445 ₂ may face each other, as shown inFIG. 5E. Note that portions 442 ₁ and 442 ₂ are covered by portions ofcharge trap 260, but are devoid of conductor, such as portions ofsemiconductor structures 455.

Source select gates 470 and drain select gates 474 have substantiallythe same (e.g., the same) cross-sections as those shown for memory cells472 in FIG. 5E. Each source select gate 470 _(2,1) includes a portion ofsemiconductor structure 455 ₂, as a channel region thereof, adjacent to(e.g., in direct contact with) the outer surface of the first portion(e.g., the corner) of the sidewall of a respective pillar 445 ₂, aportion of a charge trap 260 adjacent to the portion of semiconductorstructure 455 ₂, and a control gate 465 _(1,1) adjacent to the portionof charge trap 260, as shown in FIG. 4E. Each source select gate 470_(2,2) includes a portion of the other semiconductor structure 455 ₂, asa channel region thereof, adjacent to (e.g., in direct contact with) theouter surface of the second portion (e.g., the opposite corner) of thesidewall of the respective pillar 445 ₂, an other portion of the chargetrap 260 adjacent to the portion of the other semiconductor structure455 ₂, and a control gate 465 _(1,2) adjacent to the other portion ofthe charge trap 260, as shown in FIG. 4E. For example, a source selectgate 470 _(2,1) and a source select gate 470 _(2,2) may wrap aroundportions of the sidewall of a pillar 445 ₂ in a manner similar to thatshown in FIG. 5E for memory cells 472 _(2,1) and 472 _(2,2). Note thatfour source select gates respectively wrap around the four corners of apillar structure 435, e.g., and as such, may be termed “quarter-wrap”source select gates.

Each drain select gate 474 _(2,1) includes a portion of semiconductorstructure 455 ₂, as a channel region thereof, adjacent to (e.g., indirect contact with) the outer surface of the first portion (e.g., thecorner) of the sidewall of a respective pillar 445 ₂, a portion of acharge trap 260 adjacent to the portion of semiconductor structure 455₂, and a control gate 465 _(3,1) adjacent to the portion of charge trap260, as shown in FIG. 4E. Each drain select gate 474 _(2,2) includes aportion of the other semiconductor structure 455 ₂, as a channel regionthereof, adjacent to (e.g., in direct contact with) the outer surface ofthe second portion (e.g., the opposite corner) of the sidewall of therespective pillar 445 ₂, an other portion of the charge trap 260adjacent to the portion of the other semiconductor structure 455 ₂, anda control gate 465 _(3,2) adjacent to the other portion of the chargetrap 260, as shown in FIG. 4E. For example, a drain select gate 474_(2,1) and a drain select gate 474 _(2,2) may wrap around portions ofthe sidewall of a pillar 445 ₂ in a manner similar to that shown in FIG.5E for memory cells 472 _(2,1) and 472 _(2,2). Note that four drainselect gates respectively wrap around the four corners of a pillarstructure 435, e.g., and as such may be termed quarter-wrap drain selectgates. The source and drain select gates can be programmable and may beprogrammed or left unprogrammed.

Note that a word line 480 ₁ is commonly coupled to the memory cells 472_(1,1) and 472 _(2,1) respectively on different pillars 445 ₁ and 445 ₂,and a word line 480 ₂ is commonly coupled to the memory cells 472 _(1,2)and 472 _(2,2) respectively on those different pillars 445 ₁ and 445 ₂,as shown in FIG. 5E.

Referring to FIG. 3D, the access-line (e.g., word-line) pitchWL_(Pitch200) and the data-line (e.g., bit-line) pitch BL_(Pitch200) areshown for memory array 200. The word-line pitch WL_(Pitch200) may beexpressed as

WL _(Pitch200) =WS+2(R+W)+CTF+Tsi  (1)

and the bit-line pitch BL_(Pitch200) may be expressed as

BL _(Pitch200) =W+2Tsi+2CTF+OD  (2)

where the distances WS, (R+W), CTF, W, and Tsi are shown in FIG. 3D.

The bit-line pitch may be the pitch of the memory cells commonly coupledto a word line, e.g., in the word-line direction, while the word-linepitch may be the pitch of the memory cells in the bit-line direction.Note that the thickness of a semiconductor structure 255 (e.g., the termTsi) occurs twice in the pitch BL_(Pitch200).

Referring to FIG. 5E, the access-line (e.g., word-line) pitchWL_(Pitch400) and the data-line (e.g., bit-line) pitch BL_(Pitch400) areshown for memory array 400. The word-line pitch WL_(Pitch400) may beexpressed as

WL _(Pitch400) =WS+2(R+W)+CTF+Tsi  (3)

and the bit-line pitch BL_(Pitch400) may be expressed as

BL _(Pitch400=)0.5PS+0.5W+(R+W)+Tsi+CTF  (4)

where the distances WS, (R+W), CTF, PS, W, and Tsi are shown in FIG. 5E.The distance PS may be substantially the same (e.g., the same as) WS.Note that the thickness of a semiconductor structure 455 (e.g., the termTsi) occurs once in the pitch BL_(Pitch400).

FIG. 6 is a cross-sectional view (cross-hatching omitted) of a memoryarray 600, as viewed from the top, according to the prior art. FIG. 6 isanalogous to the views of FIGS. 3D and 5E. Memory array 600 includes aplurality of memory cells 672 that are coupled to access lines, e.g.,word lines 680. Each memory cell 672 is completely wrapped around asidewall (e.g., the perimeter) of a pillar 635 that may be formed from adielectric. As such, a memory cell 672 may be termed a “full-wrap”memory cell, as compared with the “half-wrap” memory cells 272 of memoryarray 200 in FIG. 3D and the “quarter-wrap” memory cells 472 of memoryarray 400 in FIG. 5E. A string of series coupled memory cells 672 isformed adjacent to each pillar 635, i.e., one string per pillar 635.

Each memory cell 672 includes a semiconductor 614 formed adjacent to andcompletely wrapped around a respective pillar 635. A charge trap 660 isformed adjacent to and is completely wrapped around a respectivesemiconductor 614. A control gate 665 that forms a portion of arespective word line 680 is formed adjacent to and is completely wrappedaround a respective charge trap 660.

The access-line (e.g., word-line) pitch WL_(PitchPA) and the data-line(e.g., bit-line) pitch BL_(PitchPA) are shown for memory array 600 inFIG. 6. The word-line pitch WL_(PitchPA) may be expressed as

WL _(PitchPA) =WS+2(R+W)+2CTF+2Tsi+OD  (5)

and the bit-line pitch BL_(PitchPA) may be expressed as

BL _(PitchPA) =W+2CTF+2Tsi+OD  (6)

where the distances WS, (R+W), CTF, OD, W, and Tsi are shown in FIG. 6.For typical values of CTF=20 nm, Tsi=10 nm, OD=30 nm, WS=30 nm, R=10 nm,and W=10 nm, WL_(PitchPA)=160 nm and BL_(PitchPA)=100 nm.

The word-line pitches WL_(Pitch200) and WL_(Pitch400) respectively givenby equations (1) and (3) for memory arrays 200 and 400 are the same.Subtracting either of equations (1) and (3) from equation (5) gives thedifference between the word-line pitch WL_(PitchPA) of the “full-wrap”memory cells of the prior art and the word-line pitches WL_(Pitch200)and WL_(Pitch400) respectively for the “half-wrap” and “quarter-wrap”cells to be

ΔWL _(Pitch) =CTF+Tsi+OD  (7)

which is clearly greater than zero.

For typical values of CTF=20 nm, Tsi=10 nm, and OD=30 nm, ΔWL_(Pitch)=60nm. That is, the word-line pitch for the “half-” and “quarter-wrap”memory cells is expected to be about 38 percent less than the word linepitch for the “full-wrap” memory cells of the prior art, based on thetypical values.

Subtracting equation (2) from equation (6) shows that that the bit-linepitch BL_(PitchPA) of the “full-wrap” memory cells of the prior art andthe bit-line pitch BL_(Pitch200) for the “half-wrap” cells are the same.Subtracting equation (4) from equation (6) gives the difference betweenthe bit-line pitch BL_(PitchPA) of the “full-wrap” memory cells of theprior art and the bit-line pitch BL_(Pitch400) for the “quarter-wrap”cells of memory array 400 to be

ΔBL _(Pitch(PA-400)) =CTF+Tsi+OD−0.5PS−R−0.5W  (8)

In spite of the negative terms, equation (8) still typically gives anumber greater than zero. For example, for typical values of CTF=20 nm,Tsi=10 nm, OD=30 nm, PS=30 nm, R=10 nm, and W=10 nm,ΔBL_(Pitch(PA-400))=30 nm. That is, the bit-line pitch for the“quarter-wrap” memory cells is expected to be about 30 percent less thanthe bit-line pitch for the “full-wrap” memory cells of the prior art,based on the typical values. Note that since the bit-line pitch of the“full-wrap” memory cells of the prior art and the bit-line pitch for the“half-wrap” cells are the same, the bit-line pitch for the“quarter-wrap” memory cells is expected to be about 30 percent less thanthe bit-line pitch for the “half-wrap” memory cells. For embodimentsinvolving dielectric pillars, this is due, at least in part, to the factthat adjacent quarter-wrap” memory cells in the word line direction andcommonly coupled to a single word line 480 are located adjacent topillars 445 ₁ and 445 ₂ (FIG. 5E) that are formed from a singledielectric pillar structure 435 (FIG. 5B) formed in a single opening,whereas adjacent half-wrap” memory cells in the word line direction andcommonly coupled to a single word line 280 are located adjacent toseparate pillars 235 (FIG. 3D) that are formed from separate dielectricsformed in separate openings.

CONCLUSION

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe embodiments will be apparent to those of ordinary skill in the art.Accordingly, this application is intended to cover any adaptations orvariations of the embodiments.

1. A memory array, comprising: first and second substantially verticalsemiconductor structures; a plurality of first memory cells coupled inseries by the first semiconductor structure, each first memory cellcomprising a first portion of a charge trap adjacent to the firstsemiconductor structure and a first control gate adjacent to the firstportion of the charge trap; and a plurality of second memory cellscoupled in series by the second semiconductor structure, each secondmemory cell comprising a second portion of the charge trap adjacent tothe second semiconductor structure and a second control gate adjacent tothe second portion of the charge trap; wherein each first control gateis electrically isolated from each second control gate.
 2. The memoryarray of claim 1, wherein the first and second semiconductor structuresare adjacent to a dielectric pillar.
 3. The memory array of claim 2,wherein the charge trap is wrapped completely around the dielectricpillar and the first and second semiconductor structures.
 4. The memoryarray of claim 3, wherein portions of the dielectric pillar are devoidof any semiconductor structure.
 5. The memory array of claim 3, whereina third portion of the charge trap is between the first and secondsemiconductor structures.
 6. The memory array of claim 5, wherein thethird portion of the charge trap is in direct contact with thedielectric pillar.
 7. The memory array of claim 2, wherein the firstsemiconductor structure is between the first portion of the charge trapand the dielectric pillar and the second semiconductor structure isbetween the second portion of the charge trap and the dielectric pillar.8. The memory array of claim 1, wherein a third portion of the chargetrap is between the control gates of successively adjacent first memorycells and between the control gates of successively adjacent secondmemory cells.
 9. The memory array of claim 1, wherein each of thecontrol gates is electrically isolated from a successive control gate inits string by a dielectric.
 10. The memory array of claim 9, wherein athird portion of the charge trap is over at least a portion of eachdielectric.
 11. The memory array of claim 1, wherein the first andsecond semiconductor structures are connected together at their bottoms.12. A memory array, comprising: first and second substantially verticalsemiconductor structures; a first string of series-coupled first memorycells, each first memory cell comprising a first charge storagestructure adjacent to the first semiconductor structure and a firstcontrol gate adjacent to the first charge storage structure; and asecond string of series-coupled second memory cells, each second memorycell comprising a second charge storage structure adjacent to the secondsemiconductor structure and a second control gate adjacent to the secondcharge storage structure; wherein no control gates are interposedbetween the semiconductor structures.
 13. The memory array of claim 12,wherein the first and second charge storage structures form portions ofa single continuous charge trap.
 14. The memory array of claim 13,wherein the first and second semiconductor structures are adjacent to adielectric pillar, and wherein the single continuous charge trap iswrapped completely around the dielectric pillar and the first and secondsemiconductor structures.
 15. The memory array of claim 12, wherein thefirst semiconductor structure forms a channel region for the firststring of series-coupled first memory cells and the second semiconductorstructure forms a channel region for the second string of series-coupledsecond memory cells.
 16. A memory array, comprising: first and seconddielectric pillars; separated first and second semiconductor structuresadjacent to each of the first and second dielectric pillars; a firststring of series-coupled first memory cells adjacent to the firstsemiconductor structure adjacent to the first dielectric pillar; asecond string of series-coupled first memory cells adjacent to the firstsemiconductor structure adjacent to the second dielectric pillar,wherein at least one first memory cell from the first string ofseries-coupled first memory cells and at least one first memory cellfrom the second string of series-coupled first memory cells are coupledto a first common access line; a first string of series-coupled secondmemory cells adjacent to the second semiconductor structure adjacent tothe first dielectric pillar; and a second string of series-coupledsecond memory cells adjacent to the second semiconductor structureadjacent to the second dielectric pillar, wherein at least one secondmemory cell from the first string of series-coupled second memory cellsand at least one second memory cell from the second string ofseries-coupled second memory cells are coupled to a second common accessline that is electrically isolated from the first common access line.17. The memory array of claim 16, wherein the first and seconddielectric pillars are formed from a dielectric formed in a singleopening.
 18. The memory array of claim 16, wherein at least one firstmemory cell from the first string of series-coupled first memory cellscomprises a first charge storage structure adjacent to the firstsemiconductor adjacent to the first dielectric pillar and at least onesecond memory cell from the first string of series-coupled second memorycells comprises a second charge storage structure adjacent to the secondsemiconductor adjacent to the first dielectric pillar, wherein the firstand second charge storage structures form portions of a singlecontinuous charge trap that is wrapped completely around the firstdielectric pillar.
 19. The memory array of claim 16, wherein nosemiconductor structures are between the first and second pillars.
 20. Amemory array, comprising: first and second substantially verticalsemiconductor pillars; a first string of series-coupled first memorycells, each first memory cell comprising a first charge trap that wrapscompletely around the first semiconductor pillar and a first controlgate adjacent to the first charge trap; and a second string ofseries-coupled second memory cells, each second memory cell comprising asecond charge trap that wraps completely around the second semiconductorpillar and a second control gate adjacent to the second charge trap;wherein no control gates are interposed between the first and secondsemiconductor pillars.
 21. The memory array of claim 20, furthercomprising a dielectric between the first and the second charge traps.22. A method of forming a memory array, comprising: forming an openingthrough alternating first and second dielectrics; forming asemiconductor within the opening; removing a portion of thesemiconductor to form first and second semiconductor pillars from thesemiconductor; forming a first charge storage structure adjacent to andthat wraps completely around the first semiconductor pillar; forming asecond charge storage structure adjacent to and that wraps completelyaround the second semiconductor pillar; forming a plurality of firstconductors adjacent to the first charge storage structure; wherein thefirst conductors respectively define first memory cells that are coupledin series by the first semiconductor pillar; and forming a plurality ofsecond conductors adjacent to the second charge storage structure;wherein the second conductors respectively define second memory cellsthat are coupled in series by the second semiconductor pillar.
 23. Themethod of claim 22, further comprising forming a dielectric between thefirst and the second charge storage structures.
 24. The method of claim22, wherein there is no conductor between the first and the secondsemiconductor pillars.
 25. The method of claim 22, further comprisingremoving the first dielectrics before forming the charge storagestructure, wherein forming the charge storage structure furthercomprises forming the charge storage structure adjacent to the seconddielectrics.